As shown in FIGS. 1 and 2, a discharge processing machine 10 of the prior art comprises a machine base 11, a work platform 12 mounted at the front end of the machine base 11 such that the work platform 12 is capable of sliding horizontally along the XY axes, a machine head seat 13 mounted on the rear end of the machine base 11 and provided with a fixation arm 14 extending toward the Y axis of the machine base 11. The fixation arm 14 is provided at the front end thereof with a connection portion 14A which is provided at the top thereof with a servomotor 14B. A fixation seat 15 is fastened with the front end of the connection portion 14A and is provided at the top end thereof with a fixation plate support 15A with a belted wheel 15B being pivoted thereto such that the belted wheel 15B is connected with the rotary shaft 14C of the servomotor 14B by a belt 15C. A main shaft seat 16 is mounted on the fixation seat 15 such that the main shaft seat 16 is capable of sliding along the Z axis corresponding to the normal line of the work platform 12. The main shaft seat 16 is provided with a nut 16A engaging a threaded rod 16B which is fastened at one end thereof with the center of the belted wheel 15B. The threaded rod 16B is actuated by the servomotor 14B to turn clockwise or counterclockwise, so as to control the position of the main shaft seat 16 moving along the Z axis to facilitate the fastening of the lower end of the main shaft seat 16 with a discharge processing head (not shown in the drawings). A workpiece (not shown in the drawings) fixed on the work platform 12 can be thus processed.
Such a prior art discharge processing machine 10 as described above is defective in design in that the servomotor 14B is mounted on the top of the connection portion 14A of the fixation arm 14, and that the belted wheel 15B is actuated by the servomotor 14B to turn to control the advancing of the main shaft seat 16. In light of the belted wheel 15B being mounted in the fixation plate support 15A, the underside of the fixation plate support 15A forms an upper dead point of the moving range of the main shaft seat 16. With a view to increasing the moving range of the main shaft of the prior art discharge processing machine 10, the main shaft seat 16, the threaded rod 16B, the connection portion 14A, and the fixation seat 15 are all increased in length so as to enable the top of the connection portion 14A and the fixation plate support 15A to have a higher horizontal position to facilitate the assembly of the servomotor 14B and the belted wheel 15B at the expense of the material cost as well as the processing cost. In addition, the processing machine 10 is so cumbersome that it must be disassembled to facilitate the shipping of the processing machine 10. On arrival at the shipping destination, the processing machine 10 must be assembled and calibrated at additional cost.